Five rules I try to live by:
1) Don't view this as a "diet." View it as a permanent change in your life. Cliche, but true.
2) Don't kill yourself about a bad day. You're going to have them. Just get in the saddle again the next day and get back to your new normal.
3) Get support from anywhere you can find it -- family, friends, the internet, etc. This also means getting your significant other to remove poisonous foods from your household. My dear wife of 31 years took out every cancy, cookie, chocolate, cracker, and potato chip.
4) Set short term and long term goals. My long term goal will take 2 1/2 years when I'm done, but I have a short term goal of losing 2 pounds a month. I also have goals regarding my blood pressure, BMI, pulse, along with weight lifting goals. Making a goal is very motivational.
5) DON'T skip meals. Figure out how many calories you need to be in a 300 to 700 calorie deficit per day, and then space the food out so you're never hungry. When your stomach starts growling from hunger, you're likely to cave in to your temptation.
I can't say I've really succeeded yet -- I've been doing this since July of last year. But so far I've made good progress. I know the real test will be keeping the weight off for the long term.